A variation in the effective diffusion coefficient, from 2.0 x 10−7 to 1.1 x 10−5cm2/s, was detected for the first time by using the back-scattering of ions, scanning electron microscopy with microanalysis (wave-length dispersive spectrometry) and nanohardness methods. Three stages were discovered in the motion of W ions. Firstly, from the coating surface to the bulk (without melting). Secondly, accelerated mass transfer to the bulk, with melting. Thirdly, sharp decreases in the peak concentration of W ions and a reversal of the direction (from the bulk to the surface).

Mass Transport of W Atoms and Variation of Stoichiometry in Al-Ni Coating as a Result of Electron Beam Irradiation. A.D.Pogrebnjak, S.M.Duvanov, B.P.Gritsenko, N.A.Pogrebnjak, M.K.Kylyshkanov: Technical Physics, 2007, 52[11], 1502-5